I like both cars & prefer these over civic & corolla.
Performance wise both cars are good & i m not sure about the typical problems associated to particular model but my consent is largely based on exterior, interior & apearance etc.
In diffrent models & year both cars take leads over each other as in 88~91 models Lancer is way better than Sunny.
In 96~98 models Lancer is again better then Sunny.
While in 00~02 model I dont think there is some thing better (in its class) than Sunny in pakistani market & same was again the case in 05~06 modles & sunny take the lead.
All these comprisons are as per my personal opinion.